Shell for ballistic helmet

ABSTRACT

A shell for ballistic helmet formed from a plurality of paraaramide fabric layers such as KEVLAR-KM2®, and bonding resin. All fabric layers have areal density less than 200 g/m 2 , preferably part of them have areal density less than 160 g/m 2 . The number of paraaramide layers is greater than 28, preferably 38 and more. The bonding resin constitutes less than 12% of the shell weight. The shell has average thickness less than 6.5 mm and average areal density less than 7.5 Kg/m 2 . A method for the production of such shells includes pressing and bonding the plurality of layers at pressure equal to or above 150 Kg/cm 2 , preferably above 300 Kg/cm 2 .

FIELD OF THE INVENTION

This invention relates to shells for ballistic helmets, and moreparticularly to helmet shells made of paraaramide fabrics such asKevlar®, protecting from bullets and fragments.

BACKGROUND OF THE INVENTION

A shell for ballistic helmet is supposed to stop incident shrapnelfragments or bullets, thereby protecting the head of the user. The aimof shell design and manufacture is to obtain a shell providing requiredballistic protection at minimal weight. The weight of the shell is ofgreat importance because the helmet user carries it for long periods oftime, and the lighter the helmet, the more it is convenient in use.

The ballistic protection of the helmet is normally tested by theso-called V50 test, 17 grain, according to known US and Europeanstandards. The test measures the velocity at which 50% of fragmentspierce the helmet while 50% are retained. An average areal density ofthe shell material is the weight of the shell divided by its area. Theratio between the level of ballistic protection and the areal density isthe decisive parameter determining the helmet quality, and in general ifit is higher, then the helmet is better. This ratio is called protectioncoefficient:

Protection coefficient=V50/areal density

An additional parameter is the thickness of the shell. The smaller thethickness, the less awkward is the helmet and more convenient it is inusage.

One of the most common technologies for production of ballistic helmetshells is pressure forming of the shells in a mold, from a stack ofparaaramide fabric blanks with bonding resin. The manufacturers areknown to use up to 16-24 layers of fabric with 220 to 300 g/m² arealdensity, and bonding resin in about 14-20% of the total shell weight.The stack of blanks soaked with resin is pressed in a mold at about30-40 Kg/cm² pressure at temperature suitable for the resinpolymerization. The obtained shells have more than 8-9 Kg/m² arealdensity, 7.5-9 mm thickness, and the shell weight is not less than 0.850Kg.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a shell forballistic helmet formed from a plurality of paraaramide fabric layersand bonding resin. The fabric layers have areal density less than 200g/m², the shell has average thickness less than 6.5 mm and average arealdensity less than 7.5 Kg/m². Preferably, part of the fabric layers haveareal density less than 160 g/m², while the rest fabric layers haveareal density between 200 and 160 g/m². The number of paraaramide layersshould be greater than 28, preferably not less than 33, more preferably38 and more, at least part of the layers having areal density notexceeding 160 g/m².

Preferably, the bonding resin constitutes less than 12% of the shellweight.

The present invention is based on a surprising discovery of theinventors that, if in a shell for a ballistic helmet formed from aplurality of paraaramide fabric layers and bonding resin, considerablygreater number of layers is used than that known heretofore with a lowerareal density (weight) of the layers than that typically used in thepractice, the shell yields the required ballistic protection at lighterweight than conventional helmet shells, or better ballistic protectionwith the same shell weight. Another contributing factor is the usage oflayers with different areal density.

According to another aspect of the present invention, there is provideda method for the production of shells for ballistic helmets from aplurality of layers as described above, the method including pressingand bonding the plurality of layers at pressure equal to or above 150Kg/cm², preferably above 300 Kg/cm².

The composition and method of production according to the presentinvention provide for lighter helmets with better ballistic protectionqualities. For example, a shell with less than 0.7 Kg weight and levelof protection higher than V50=2000 ft/sec can be manufactured.

DETAILED DESCRIPTION OF THE INVENTION

One example of the material used for the production of a shell accordingto the present invention is a material made of 38-40 layers ofKEVLAR®-KM2 and/or other paraaramide fabric having areal densityrespectively 155 g/m² and 195 g/m² and bound by bonding resin of about10-12% of the shell weight. The KEVLAR®-KM2 fabric is used mainly in theexternal layers of the shell.

The above shell structure is manufactured by pressing the stack ofblanks to 6 mm thickness using pressures of 150 to 300 Kg/cm².

A prototype ballistic helmet shell with the inventive structure,manufactured by the above method weights 0.7 Kg and provides for levelof protection V50=2000 ft/sec. The area of the shell is about 0.1 m².The average areal density of the shell is 0.7/0.1=7 Kg/m², and theprotection coefficient is 2000/7=286.

1. Shell for ballistic helmet formed from a plurality of paraaramide fabric layers and bonding resin, wherein said fabric layers have areal density equal or less than 200 g/m², said shell has average thickness less than 6.5 mm and average areal density less than 7.5 Kg/m².
 2. Shell according to claim 1, wherein at least one of said fabric layers has areal density less than 160 g/m².
 3. Shell according to claim 1, wherein a first part of said fabric layers have areal density less than 160 g/m² and a second part of said fabric layers have areal density between 200 and 160 g/m².
 4. (canceled)
 5. Shell according to claim 1, wherein said bonding resin constitutes less than 12% of the shell weight.
 6. Shell according to claim 1, wherein said plurality of layers is greater than
 28. 7. Shell according to claim 6, wherein said plurality of layers is not less than
 33. 8. Shell according to claim 7, wherein said plurality of layers is not less than
 38. 9. Shell for ballistic helmet formed from a plurality of paraaramide fabric layers and bonding resin, wherein said plurality of layers is greater than 28 and said shell has average thickness less than 6.5 mm.
 10. Shell for ballistic helmet formed from a plurality of paraaramide fabric layers and bonding resin, wherein said plurality of layers is not less than
 38. 11. Shell for ballistic helmet formed from a plurality of paraaramide fabric layers and bonding resin, wherein said fabric layers have areal density less than 200 g/m², and said plurality of layers is greater than
 28. 12. Shell for ballistic helmet formed from a plurality of paraaramide fabric layers and bonding resin, wherein said plurality of layers is greater than 28 and said shell has average areal density less than 7.0 Kg/m².
 13. Method of producing a ballistic helmet shell as defined in claim 12, the method including the step of pressing and bonding of said plurality of layers at a pressure equal to or above 150 Kg/cm².
 14. Method according to claim 12, wherein said pressure is equal or above 300 Kg/cm². 